Contents

From the Preface

In his Preface, Birkeland writes:

"The knowledge gained, since 1896, in radio-activity has favoured the view to which I gave expression in that year, namely, that magnetic disturbances on the earth, and aurora borealis, are due to corpuscular rays emitted by the sun.

"During the period from 1896 to 1903 I carried out, in all, three expeditions to the polar regions for the purpose of procuring material that might further confirm this opinion. I have moreover, during the last ten years, by the aid of numerous experimental investigations, endeavoured to form a theory that should explain the origin of these phenomena. It is the results of these investigations that are recorded in this work, the first volume of which treats of terrestrial magnetic phenomena- and earth-currents, this section forming the first two thirds of the volume. The second volume will treat of aurora and some results of meteorological observations made at our stations.

"The leading principle that I have followed in this work has been to endeavour always to interpret the results of the worked-up terrestrial-magnetic observations, and the observations of aurora, upon the basis of my above-mentioned theory.

"[..] experimental investigations with a little magnetic terrella in a large discharge-tube, and by mathematical analysis, we have endeavoured to prove that a current of electric corpuscles from the sun would give rise to precipitation upon the earth, the magnetic effect of which agrees well with the magnetic field of force that was found by the observations on the earth.

"[..] The mathematical investigations, which, together with my experiments, are intended to make clear the movement of electric corpuscles from the sun to the earth, have been carried out, with a perseverance and ingenuity worthy of all admiration, by my friend, Professor STORMER, who will publish the complete results of his investigations in a special part of the present work.

From the Preface (Second section)

"The experimental investigations which at first were designed to procure analogies capable of explaining phenomena on the earth, such as aurora and magnetic disturbances, were subsequently extended, as was only natural, with the object of procuring information as to the conditions under which the emission of the assumed hello-cathode rays from the sun might be supposed to take place.

"The magnetic globe was then made the cathode in the vacuum-box, and experiments were carried on under these conditions for many years.

"It was in this way that there gradually appeared experimental analogies to various cosmic phenomena, such as zodiacal light, Saturn's rings, sun-spots and spiral nebular.

"The consequence was that attempts were made to knit together all these new discoveries and hypotheses into one cosmogonic theory, in which solar systems and the formation of galactic systems are discussed perhaps rather more from electromagnetic points of view than from the theory of gravitation.

"One of the most peculiar features of this cosmogony is that space beyond the heavenly bodies is assumed to be filled with flying atoms and corpuscles of all kinds in such density that the aggregate mass of the heavenly bodies within a limited, very large space would be only a very small fraction of the aggregate mass of the flying atoms there.

"And we imagine that an average equilibrium exists in infinite space, between disintegration of the heavenly bodies on the one hand, and gathering and condensation of flying corpusles on the other.

Contents (Volume 1)

(Note: Volume 2 was never published)

Section 1

Introduction

The first Expedition, 189

The second Aurora Expedition, 1899—1900

THE EXPEDITION OF 1902--1903

The Auroral Station in Kaafjord

The Auroral Station in Dyrafjord, Iceland

The Auroral Station in Spitsbergen

The Auroral Station in Novaja Semlja

The Working-up of the Material

PART I. MAGNETIC STORMS, 1902-1903.

INVESTIGATIONS BY MEANS OF DIURNAL REGISTERINGS FROM 25 OBSERVATORIES.

CHAPTER I. PRELIMINARY REMARKS CONCERNING OUR MAGNETIC RESEARCHES.

Our Aim and our Method of Working 41

On the Calculation of the Perturbing Force 44

On the Separation of Simultaneous Perturbations 47

CALCULATION OF THE SCALE-VALUES FOR THE REGISTERINGS AT THE NORWEGIAN STATIONS.

Determin1a6t.ion of the Scale-Values for the Dcclinometer 48

Determination of the Sensibility of the Variometers for the Horizontal and Vertical Intensity

Determinations of Sensibility for Kaafjord and Bossekop 50

Determinations of Sensibility for Dyrafjord 51

Determinations of Sensibility for Axeloen 53

Determinations of Sensibility for Matotchkin Schar 54

Temperature Coefficients for the Registerings 55

Explanation of the Charts 56

The topics of the Magnetic Registerings, Explanation and General Remarks 58

CHAPTER II. ELEMENTARY PERTURBATIONS.

General Remarks 61

The Equatorial Perturbations 62

The Positive Equatorial Perturbation . The Perturbation of the 26th January 1903 .

The Perturbations of the 9th December, 1902 70

The Perturbation of the 23rd October, 1902 76

Concerning the Cause of the Positive Equatorial Perturbation 78

The Negative Equatorial Storms 83

The Polar Elementary Storms • •

The Typical Field for the Polar Elementary Storms 85

The Perturbation of the 15th December, 1902 87

Concerning the Cause of the Perturbation 95

The Perturbation of the l0th February, 1903 io6

Concerning the Cause of the Perturbation 113

The Perturbations of the 3oth and 31st March, 1903 115

The Perturbations of the 22nd March, 1903 127

The Perturbations of the 26th December, 1902 137

Cyclo-Median Storms

The Perturbation of the 6th October, 1902 145

Concerning the Cause of the Perturbation 1 49

Further Comparison with Stormer's Mathematical Theory

CHAPTER III. COMPOUND PERTURBATIONS.

The Perturbation of the 29th and 30th October, 1902 161

The Perturbation of the 25th December, 1902 164

The Perturbation of the 28th December, 1902 169

The Perturbations of the 15th February, 1903 172

The Perturbations of the 7th and 8th February, 1902 187

The Perturbations of the 27th and 28th October, 1902 209

The Perturbations of the 28th and 29th October, 1902 222

The Perturbations of the 31st October and 1st November, 1902 230

How these Perturbations may be explained 234

The Perturbations of the 11th and 12th October, 1902 251

Concerning the Cause of the Perturbations . Positive and negative Polar Storms

The Perturbations of the 23rd and 24th November, 1902 272

The Perturbations of the 26th and 27th January, 1903 286

Further Comparison with the Terrella-Experiments 297

CHAPTER IV. CONCERNING THE INTENSITY OF THE CORPUSCULAR PRECIPITATION IN THE ARCTIC REGIONS OF THE EARTH.

Development of General Formula 303

Numerical Values for Height and Strength of Current 306

The Energy of the Corpuscular Precipitation . The Source of the Sun's Heat 311

Section 2

PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS.

CHAPTER I. POLAR MAGNETIC STORMS 1882--1883.

The Treatment of the Observations from the Polar Expedition of 1882 & 1883

The Perturbation of the 15th January, 1883 323

The Perturbations of the 2nd January, 1883 339

The Perturbations of the 1st November, 1882 350

The Perturbations of the 14th and 15th February, 1883 361

The Perturbations of the 15th July, 1883 371

The Perturbations of the 1st February, 1883 386

The Perturbations of the 15th December, 1882 397

The Perturbations of the 15th October, 1882 412

CHAPTER II. MATHEMATICAL INVESTIGATIONS. PRELIMINARY RESUME.

The Calculation of the Field of Force for the assumed Polar Current-System 423